Find the next number in the series: 5, 10, 20, 40, ? MCQ with Answer and Explanation

Explanation:
Each letter is shifted one place forward: M→N, O→P, B→C, I→J, L→M, E→F = NPCJMF.

Explanation:
Each letter is shifted two places forward: R→T? Wait R+2=T. Let's check OCEAN: O+2=Q? O is 15 +2=17 Q, not P. Need fix. Use shift +1? O→P, C→D? C+1=D not E. Pattern not valid. Better replace question. Use simple shift +1: OCEAN → PDFBO? O+1=P, C+1=D, E+1=F, A+1=B, N+1=O = PDFBO. Then RIVER → SJWFS. We'll not use that broken question. Instead create valid coding.

Explanation:
'colour' common first two =5. 'chalk' first and third =2.